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Sound Bytes: Out to sea and off to the races

March 03, 2022

Revamping our buoy design

Anne and Jack secure poles to the back of a small boat as they prepare to go out to sea. Anne and Jack secure buoys on the small boat as they prepare to go out to sea. Credit: C. Hom-Weaver/NOAA Fisheries

We need high quality acoustic data to study a variety of marine mammals that produce a huge range of sounds. In a previous Sound Bytes post, Cory described a low-frequency noise that interfered with her ability to detect fin whales in some of our archived recordings. Our team investigated the source of the noise in the lab, and suspected that the buoy movement in the water was causing the noise. We came up with a few ideas to reduce buoy movement underwater, and then Cory, Jack and I put them to the test in the open ocean of Monterey Bay. We were off to the races! Except this time instead of cheering for the fastest, we were all curious who would be the slowest, quietest buoy. 

Three different buoys floating at the surface. The lft buoy has a red float at the bottom of a tall aluminum pole. The middle buoy has a small red buoy submerged below a black pole. The right buoy has a thick yellow ring around a white PVC tube.
Three buoy surface configurations that were tested during sea trials in Monterey Bay, California. Original tall buoy (left), "Ogger" (middle), low-profile (right). Credit: C. Hom-Weaver/NOAA Fisheries

On Day 1 of the races, we tested three different surface configurations to compare how they moved through the water. Our original design has a tall metal radar reflector and giant red buoy. We suspected these features might catch the wind, act as sails and cause the buoy to speed through the water. The second design we call the "Ogger" because it was designed by the crab fisherman Dick Ogg (see Shannon’s blog). The Ogger had a smaller buoy and radar reflector. Our third buoy had a much lower profile, like a tortoise, which might make it slower and steadier than the others. We tracked the movement of the buoys by following their GPS trackers, which gave us position updates every 5 minutes. In the first 5 hours, the Ogger was in the lead, but all three buoys traveled an average of 0.25 miles per hour. This race is obviously not for speed! 

An underwater parachute is held up in the air with the ocean in the background.
Underwater parachute used to slow the movement of the buoy through the water. Credit: A. Simonis/NOAA Fisheries

On Day 2, we revisited each buoy in the morning to add bungies and underwater parachutes, which we call drogues. These additions should reduce movement through the water. Overall, we were thinking that less movement would produce less noise in our recordings.  Would the parachutes slow the tall buoys down to tortoise speed? We left the buoys to drift for the rest of the day to find out. 

While the buoys were drifting, we went out to look for whales. We found a few gray and humpback whales, and were able to take some photos. Although they’re not exactly glamor shots, these photos are very useful to researchers. Each individual can be recognized by the shape of their dorsal fin and markings on their body. We will share our photos with our partners at Cascadia Research Collective, who will look for matches in their photo-id catalogs. We also collected opportunistic acoustic recordings of Risso’s dolphins, which will be used to train machine learning algorithms. We really try to make the most out of our precious time on the water. 

The edge of a gray whales back rises above the water, showing unique white and gray patches on the skin. The rocky coast of Carmel, California is visible in the distance.
The back of a gray whale as it swims by the coast of Carmel, California. Credit: C. Hom-Weaver/NOAA Fisheries. NOAA Permit #21678-01
The left side of a humpback whale's body and dorsal fin rise above the water.
The back of a humpback whale with Point Pinos in the distance. Credit: C. Hom-Weaver/NOAA Fisheries. NOAA Permit #21678-01

We ended the race as the wind was picking up and light fading on Day 2. The GPS tracks agreed. The low-profile buoy had the lowest average speed through the water, with and without the drogue. However, we know that this design is hard for passing ships to see, and has a higher risk to be hit and sunk. In addition to speed and visibility, next we will review the noise in the recordings to determine the official winner. With each iteration, our buoy design is improving. Better data means more information for science-based decision making and hopefully, better conservation outcomes for humans and the whales.   

Two charts showing buoy speed through the water without the drogue (left) and with the drogue (right). Speed (miles per hour) shown on y-axis, ranging from 0.2-0.5 miles per hour. Dates and times are shown on the x-axis. The buoy speed is shown in red (Ogger), green (Original) and blue (Low-Profile).
The buoy speed for each surface configuration (red=Ogger, green=Original, blue=Low-profile), without drogues (left) and with drogues (right). Credit: NOAA Fisheries

 This work was conducted in the Monterey Bay National Marine Sanctuary under permit number MULTI-2019-005 and was funded in part by the Bureau of Ocean Energy Management and NOAA Fisheries’ Southwest Fisheries Science Center. 

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Last updated by Southwest Fisheries Science Center on March 07, 2022